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Simple & Compound Interest
· Formula🧮 Formula Reference Sheet
SI = (P × R × T) ÷ 100 CI = P × (1 + R/100)^T − P Amount (CI)= P × (1 + R/100)^T Rule of 72 : Doubling time ≈ 72 ÷ R CI−SI (2yr): P × (R/100)² CI−SI (3yr): P × (R/100)² × (R/100 + 3)
⚡ Example per formula
SI = (P × R × T) ÷ 100
↳₹5000 × 8% × 3 yr / 100 = ₹1200
CI = P × (1 + R/100)^T − P
↳₹10000 × (1.10)² − 10000 = ₹2100
Amount (CI)= P × (1 + R/100)^T
↳₹10000 × (1.10)² = ₹12100
Rule of 72 : Doubling time ≈ 72 ÷ R
↳At 12% money doubles in 72/12 = 6 years
CI−SI (2yr): P × (R/100)²
↳₹5000 × (10/100)² = ₹50
CI−SI (3yr): P × (R/100)² × (R/100 + 3)
↳₹4000 × (0.1)² × 3.1 = ₹124
✏️ Worked Example
Find the simple interest on ₹6000 at 8% per annum for 3 years.
👁 Show step-by-step solution
SI = (6000 × 8 × 3) / 100 = 144000 / 100 = ₹1440 ✅ Answer: ₹1440
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